
/*********************************************************************************
* Class for providing usefull functions when operating on battery power
**********************************************************************************/


class battery_c
{
  
  public:

  long readVcc() {
    // Read 1.1V reference against AVcc
    // set the reference to Vcc and the measurement to the internal 1.1V reference
    #if defined(__AVR_ATmega32U4__) || defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
      ADMUX = _BV(REFS0) | _BV(MUX4) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
    #elif defined (__AVR_ATtiny24__) || defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__)
      ADMUX = _BV(MUX5) | _BV(MUX0);
    #elif defined (__AVR_ATtiny25__) || defined(__AVR_ATtiny45__) || defined(__AVR_ATtiny85__)
      ADMUX = _BV(MUX3) | _BV(MUX2);
    #else
      ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
    #endif  
   
    delay(2); // Wait for Vref to settle
    ADCSRA |= _BV(ADSC); // Start conversion
    while (bit_is_set(ADCSRA,ADSC)); // measuring
   
    uint8_t low  = ADCL; // must read ADCL first - it then locks ADCH  
    uint8_t high = ADCH; // unlocks both
   
    long result = (high<<8) | low;
   
    result = 1125300L / result; // Calculate Vcc (in mV); 1125300 = 1.1*1023*1000
    return result; // Vcc in millivolts
  }
};

battery_c Battery;
